The same researchers who first found a link between exposure to low-frequency electromagnetic fields (EMFs: ordinary magnetic fields generated by "pretty much anything that uses electricity") and miscarriage have extended their research and found that the higher the exposure in utero, the greater a child's risk of asthma years later. Dr. De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente Division of Research, followed up with the women who first wore monitors during their pregnancies years ago. The women were unable to see their own levels of exposure, and recorded for researchers nothing more than basic information about their daily whereabouts: at home and not in bed, at home in bed, at work, traveling and other.
Li's team found little difference in EMF levels at any location, but still attributed the most exposure to common household appliances (for unexplained reasons) and suggested that women try to limit their exposure. Here's the helpful quote from the Time magazine article on the research: "Don't stand in front of the microwave when it's heating food, for example, and hold the hair dryer as far away from your belly as possible, or switch to a dryer that's battery operated."